1. Field of the Invention
The present invention relates to a microcontroller, and more particularly, to a microcontroller including a plurality of functional blocks.
2. Description of the Related Art
In a conventional microcontroller, controlling supply/stop of a clock signal to each of functional blocks associated with input/output ports is effected by a controlling register provided for each of the input/output ports. In the conventional microcontroller, a central processing unit (CPU) executes a program, and the controlling registers are set according to results of the execution. Then, supply/stop of the clock signals to the functional blocks is controlled by setting the controlling registers.
However, in the conventional microcontroller, each of the input/output ports needs to be provided with the controlling register, and therefore, a problem exists that an overall size of the microcontroller becomes large. Further, after the microcontroller has been reset, the controlling registers are not set until the CPU executes the program, and therefore, functional setting of the input/output ports has not yet performed immediately after the reset of the microcontroller. Some types of external ICs being connected to the input/output ports require that the input/output ports are set immediately after the reset of the microcontroller and the microcontroller outputs a predetermined signal. In this case, the conventional microcontroller has a problem that it cannot output a predetermined signal immediately after being reset.